WO2016068293A1 - Aluminum alloy substrate for magnetic disk - Google Patents

Abstract

This aluminum alloy substrate for a magnetic disk contains 0.5-24.0 mass% of Si and 0.01-3.00 mass% of Fe and comprises the balance being Al and inevitable impurities. The aluminum alloy substrate for a magnetic disk has a smooth and highly rigid plated surface.

Description

Aluminum alloy substrate for magnetic disk

The present invention relates to an aluminum alloy substrate for a magnetic disk.

An aluminum alloy magnetic disk used for a storage device of a computer has a good plating property and excellent mechanical properties and workability. JIS5086 (Mg of 3.5% to 4.5% by mass, 0.50%) Fe in mass% or less, Si in 0.40 mass% or less, Mn in 0.20 mass% to 0.70 mass%, Cr in 0.05 mass% to 0.25 mass%, 0.10 mass% (Cu, 0.15 mass% or less of Ti, 0.25 mass% or less of Zn, the balance Al and inevitable impurities). In addition, the aluminum alloy magnetic disk is designed to limit the content of impurities such as Fe and Si in JIS5086 and reduce the intermetallic compounds in the matrix for the purpose of improving pit defects due to the drop-out of intermetallic compounds in the pre-plating process. It is manufactured from an aluminum alloy substrate that has been prepared, or an aluminum alloy substrate to which Cu and / or Zn in JIS5086 is intentionally added for the purpose of improving plating properties.

A general aluminum alloy magnetic disk is manufactured by first producing an annular aluminum alloy substrate, plating the aluminum alloy substrate, and then attaching a magnetic material to the surface of the aluminum alloy substrate.

For example, an aluminum alloy magnetic disk made of the JIS 5086 alloy is manufactured by the following manufacturing process. First, an aluminum alloy having a desired chemical component is cast, the ingot is hot-rolled, and then cold-rolled to produce a rolled material having a necessary thickness as a magnetic disk. This rolled material is preferably annealed in the middle of cold rolling as required. Next, this rolled material is punched into an annular shape, and in order to remove distortion and the like caused by the manufacturing process, an aluminum alloy plate made into an annular shape is laminated, and pressurized from both sides to be annealed and flattened. Annealing is performed. Thereby, an annular aluminum alloy substrate is produced.

The annular aluminum alloy substrate thus manufactured is subjected to cutting, grinding, degreasing, etching, zincate treatment (Zn substitution treatment) as a pretreatment, and then Ni—P, which is a hard nonmagnetic metal, as a base treatment. After electroless plating and polishing the plated surface, the magnetic material is sputtered. Thereby, the magnetic disk made of aluminum alloy is manufactured.

By the way, in recent years, magnetic disks are required to have a large capacity and a high density because of the need for multimedia and the like. In order to increase the capacity, the number of magnetic disks mounted on a storage device is increasing, and accordingly, the thickness of the magnetic disk is required to be reduced.

However, if the aluminum alloy substrate for a magnetic disk is thinned, the rigidity is lowered, so that there is a problem that the magnetic head and the magnetic disk collide (head crash). This is because when the magnetic disk is rotated at high speed, an air current is generated, and the magnetic disk vibrates (fluttering) due to the air current. However, if the rigidity of the substrate is low, the vibration of the magnetic disk increases and the head changes accordingly. This is because it cannot follow. When a head crash occurs, irregularities or scratches may occur on the surface of the magnetic disk, resulting in a recording error. Therefore, high rigidity of the aluminum alloy substrate is required.

In addition, since the magnetic area per bit is further miniaturized due to the high density of the magnetic disk, even if there are fine pits (holes) on the plated surface of the magnetic disk, it causes an error when reading data. . For this reason, high smoothness with few pits is required on the plated surface of the magnetic disk.

From such circumstances, in recent years, an aluminum alloy substrate for a magnetic disk having a smooth plated surface and high rigidity has been strongly desired and studied. For example, in Patent Document 1, when Mn and Zr are added to an Al—Mg-based alloy, the recrystallization temperature of the aluminum alloy substrate is raised and the recrystallization is suppressed to increase the strength, and when the magnetic head collides with the magnetic disk. Describes a method that does not cause fine irregularities.

Japanese Patent Laid-Open No. 10-273749

However, the method disclosed in Patent Document 1 can increase the strength, but since the rigidity is low, contact between the magnetic head and the magnetic disk is unavoidable, and the unevenness or scratches on the extremely fine surface can be reduced. Absent. In addition, since it contains a large amount of Mn, there are many coarse compounds in the aluminum alloy substrate, the compounds drop off in the pre-plating process, and large pits are generated on the surface, resulting in frequent pits on the plating surface. Therefore, excellent smoothness of the target plating surface has not been obtained.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an aluminum alloy substrate for a magnetic disk having a smooth plating surface and high rigidity.

The aluminum alloy substrate for a magnetic disk of the present invention,
0.5 mass% or more and 24.0 mass% or less of Si;
0.01 mass% to 3.00 mass% Fe;
Containing
It consists of the balance Al and inevitable impurities,
It is characterized by that.

The aluminum alloy substrate for the magnetic disk is
0.005 mass% or more and 2.000 mass% or less of Cu,
Mg of 0.1% by mass or more and 6.0% by mass or less,
0.1 mass% or more and 2.0 mass% or less of Ni,
0.01 mass% or more and 2.00 mass% or less of Cr,
0.01% by mass or more and 2.00% by mass or less of Mn,
0.001 mass% or more and 0.100 mass% or less of Na,
0.001 mass% or more and 0.100 mass% or less of Sr,
0.001 mass% or more and 0.100 mass% or less of P,
One or more elements selected from the group consisting of:

The aluminum alloy substrate for the magnetic disk is
You may further contain 0.005 mass% or more and 2.000 mass% or less Zn.

The aluminum alloy substrate for the magnetic disk is
You may further contain Ti and B whose sum total is 0.005 mass% or more and 0.500 mass% or less.

The aluminum alloy substrate for the magnetic disk is
The second phase particles having a maximum diameter of more than 100μm or less 3μm is 100 / mm ² or more 50000 / mm ² may be distributed in the following distribution density.

The aluminum alloy substrate for the magnetic disk is
Second phase particles may be included, and the longest diameter of the second phase particles may be 100 μm or less.

The aluminum alloy substrate for the magnetic disk is
A skin material made of pure Al or Al—Mg alloy may be clad on both sides.

According to the present invention, an aluminum alloy substrate for a magnetic disk having a smooth plating surface and high rigidity can be provided.

It is a figure which shows the flow of the manufacturing method of the magnetic disc containing the manufacturing method of the aluminum alloy substrate for magnetic discs of the bare material which concerns on embodiment of this invention. It is a figure which shows the flow of the manufacturing method of the magnetic disc containing the manufacturing method of the aluminum alloy substrate for magnetic discs of the clad material which concerns on embodiment of this invention.

The present inventors paid attention to the rigidity of the aluminum alloy substrate and the smoothness of the plating surface, and conducted intensive investigation and research on the relationship between these characteristics and the components and structure of the aluminum alloy substrate. As a result, the present inventors have found that the Si content and Fe content of the aluminum alloy substrate have a great influence on the rigidity and the smoothness of the plating surface. It has also been found that the size and distribution density of the second phase particles (such as Si particles or Al—Fe—Si compounds) have a great influence on the rigidity and the smoothness of the plating surface. Based on these findings, the inventors have arrived at the present invention.

Hereinafter, an aluminum alloy substrate for a magnetic disk according to an embodiment of the present invention will be described in detail.

An aluminum alloy substrate for a magnetic disk is used as a single layer bare material or a three layer clad material. An alloy plate obtained by metallurgically joining two or more alloy plates different from a clad material. Here, an intermediate material of a three-layer clad material is a core material, and materials on both sides of the core material are skin materials. Further, the aluminum alloy substrate includes both a bare material and a clad material unless otherwise specified.

Hereinafter, the aluminum alloy component and the content of the core material of the bare material and the clad material constituting the aluminum alloy substrate for the Al—Si—Fe based magnetic disk according to the embodiment of the present invention will be described.

(silicon)
Si exists mainly as Si particles, and has the effect of improving the rigidity of the aluminum alloy substrate. When the Si content in the aluminum alloy is less than 0.5% by mass, the aluminum alloy has insufficient rigidity. On the other hand, when the Si content in the aluminum alloy exceeds 24.0% by mass, coarse Si particles are generated. In the case of bare material, Si particles fall off during etching, zincate treatment, cutting or grinding. Large depressions occur, and the smoothness of the plating surface is reduced. In the case of the core material of the clad material, coarse Si particles present on the side surface of the substrate fall off during etching, zincate treatment, or cutting, and a large depression is generated on the side surface of the substrate. In particular, when a large depression is generated at the boundary between the core material and the skin material on the side surface of the substrate, the adhesion between the plating and the substrate is deteriorated, and plating peeling occurs. Therefore, the Si content in the aluminum alloy is in the range of 0.5% by mass or more and 24.0% by mass or less. Further, the Si content is preferably in the range of 1.0% by mass or more and 18.0% by mass or less from the viewpoint of rigidity and rollability. More preferably, it is the range of 1.5 mass% or more and 13.0 mass% or less.

(iron)
Fe exists mainly as an Al—Fe—Si based compound and has an effect of improving the rigidity of the aluminum alloy substrate. If the Fe content in the aluminum alloy is less than 0.01% by mass, the rigidity is insufficient. On the other hand, if the Fe content in the aluminum alloy exceeds 3.00%, a coarse Al—Fe—Si compound is formed. In the case of a bare material, Al is used during etching, zincate treatment, cutting or grinding. The —Fe—Si compound falls off and a large depression is generated, and the smoothness of the plating surface is lowered. In the case of the core material of the clad material, the coarse Al—Fe—Si-based compound present on the side surface of the substrate falls off during etching, zincate treatment, or cutting, and a large depression is generated on the side surface of the substrate. In particular, when a large depression is generated at the boundary between the core material and the skin material on the side surface of the substrate, the adhesion between the plating and the substrate is deteriorated, and plating peeling occurs. Therefore, the content of Fe in the aluminum alloy is in the range of 0.05% by mass to 3.00% by mass. Moreover, the content rate of Fe has the preferable range of 0.10 to 3.00 mass%.

In order to further improve the rigidity of the aluminum alloy substrate in addition to the above-described Si and Fe, the aluminum alloy substrate for a magnetic disk is preferably 0.005% by mass or more and 2.000% by mass or less of Cu, preferably 0.1%. Mg of mass% to 6.0 mass%, preferably Ni of 0.1 mass% to 2.0 mass%, preferably 0.01 mass% to 2.00 mass% of Cr, preferably 0.00 mass%. Mn from 01% by mass to 2.00% by mass, preferably Na from 0.001% by mass to 0.100% by mass, preferably Sr from 0.001% by mass to 0.100% by mass, preferably 0 1 or 2 selected from the group consisting of 0.005 mass% or more and 0.500 mass% or less, wherein the total content of P, preferably Ti and B, is 0.001 mass% or more and 0.100 mass% or less. Elements above may also be used selectively aluminum alloy further contains. These selective elements will be described below.

(copper)
Cu exists mainly as an Al—Cu-based compound and has the effect of improving the rigidity of the aluminum alloy substrate. In addition, there is an effect that the amount of dissolved Al during the zincate treatment is reduced, and the zincate film is uniformly, thinly and densely adhered to improve the smoothness of the plating in the next step. When the content of Cu in the aluminum alloy is 0.005% by mass or more, the effect of improving rigidity and the effect of improving smoothness can be further obtained. Further, when the content of Cu in the aluminum alloy is 2.000% by mass or less, the formation of coarse Al—Cu compounds is suppressed. In the case of a bare material, it is possible to further suppress the generation of a large depression due to the Al-Cu compound dropping off during etching, zincate treatment, cutting or grinding, and to further improve the smoothness of the plating surface. it can. In the case of the core material of the clad material, during etching, zincate treatment, and cutting, the coarse Al-Cu compound on the side of the substrate is prevented from dropping off and a large dent is generated, and the boundary between the core and skin on the side of the substrate is suppressed. It is possible to further suppress plating peeling at the part. Therefore, the content of Cu in the aluminum alloy is preferably in the range of 0.005% by mass to 2.000% by mass, and more preferably in the range of 0.010% by mass to less than 2.000% by mass.

(magnesium)
Mg exists mainly as an Mg—Si compound and has an effect of improving the rigidity of the aluminum alloy substrate. When the Mg content in the aluminum alloy is 0.1% by mass or more, the effect of improving the rigidity can be further obtained. Further, when the Mg content in the aluminum alloy is 6.0% by mass or less, generation of a coarse Mg—Si compound is suppressed. In the case of a bare material, the Mg-Si compound is prevented from dropping off during etching, zincate treatment, cutting or grinding, and large depressions are generated, and the smoothness of the plating surface is further suppressed from being lowered. Can do. In the case of the core material of the clad material, the rough Mg-Si compound on the side surface of the substrate is prevented from dropping off during etching, zincate processing, or cutting, and a large dent is prevented, and the boundary between the core material on the side surface of the substrate and the skin material It is possible to further suppress plating peeling at the part. Therefore, the content of Mg in the aluminum alloy is preferably in the range of 0.1% by mass to 6.0% by mass, and more preferably in the range of 0.3% by mass to less than 1.0% by mass.

(nickel)
Ni exists mainly as an Al—Ni-based compound and has an effect of improving the rigidity of the aluminum alloy substrate. When the content of Ni in the aluminum alloy is 0.1% by mass or more, the effect of improving rigidity can be further obtained. In addition, when the content of Ni in the aluminum alloy is 2.0% by mass or less, generation of a coarse Al—Ni compound is suppressed. In the case of a bare material, the Al-Ni compound is prevented from dropping off during etching, zincate processing, cutting or grinding, and large depressions are prevented, and the smoothness of the plating surface is further suppressed from being lowered. Can do. In the case of the core material of the clad material, during etching, zincate processing, and cutting, the coarse Al-Ni compound on the side of the substrate is prevented from falling off and large dents are generated, and the boundary between the core and skin on the side of the substrate is suppressed. It is possible to further suppress plating peeling at the part. Therefore, the Ni content in the aluminum alloy is preferably in the range of 0.1% by mass or more and 2.0% by mass or less, and more preferably 0.3% by mass or more and less than 2.0% by mass.

(chromium)
Cr exists mainly as an Al—Cr-based compound and has an effect of improving the rigidity of the aluminum alloy substrate. When the Cr content in the aluminum alloy is 0.01% by mass or more, the effect of improving the rigidity can be further obtained. Further, when the content of Cr in the aluminum alloy is 2.00% by mass or less, generation of a coarse Al—Cr compound is suppressed. In the case of a bare material, the Al-Cr compound is prevented from dropping off during etching, zincate treatment, cutting or grinding, and large depressions are prevented, and the smoothness of the plating surface is further suppressed from being lowered. Can do. In the case of the core material of the clad material, during etching, zincate treatment, and cutting, the coarse Al-Cr compound on the side of the substrate is prevented from falling off and a large dent is generated, and the boundary between the core and skin on the side of the substrate is suppressed. It is possible to further suppress plating peeling at the part. Therefore, the Cr content in the aluminum alloy is preferably in the range of 0.01% by mass to 2.00% by mass, and more preferably 0.1% by mass to less than 2.0% by mass.

(manganese)
Mn exists mainly as an Al—Mn—Si compound, and has the effect of improving the rigidity of the aluminum alloy substrate. When the content of Mn in the aluminum alloy is 0.01% by mass or more, the effect of improving the rigidity can be further obtained. In addition, when the content of Mn in the aluminum alloy is 2.00% by mass or less, generation of a coarse Al—Mn—Si compound is suppressed. In the case of bare material, the Al-Mn-Si compound is prevented from dropping off during etching, zincate treatment, cutting or grinding, and large depressions are prevented, and the smoothness of the plating surface is further suppressed from decreasing. can do. In the case of the core material of the clad material, during etching, zincate processing, and cutting, the coarse Al-Mn-Si compound on the side surface of the substrate is prevented from dropping and large depressions are generated, and the core material and skin material on the side surface of the substrate are suppressed. It is possible to further suppress plating peeling at the boundary portion. Therefore, the content of Mn in the aluminum alloy is preferably in the range of 0.01% by mass to 2.00% by mass, and more preferably 0.1% by mass to less than 2.0% by mass.

In order to further improve the smoothness of the plating surface of the aluminum alloy substrate in addition to the above-described Si and Fe as the Al—Si—Fe-based alloy, preferably 0.005 mass% or more and 2.000 mass% or less of Zn. It is also possible to use an aluminum alloy further containing. This element will be described below.

(zinc)
Zn has the effect of reducing the amount of dissolved Al during the zincate treatment, and depositing the zincate film uniformly, thinly and densely and improving the smoothness and adhesion of the plating in the next step. When the Zn content in the aluminum alloy is 0.005 mass% or more, the amount of dissolved Al during zincate treatment is reduced, and the zincate film is uniformly and thinly and densely adhered, thereby improving the smoothness of plating. A further improvement effect can be obtained. Further, when the Zn content in the aluminum alloy is 2.000% by mass or less, in the case of a bare material, it is possible to further prevent the zincate film from becoming uniform and the smoothness of the plating surface from being lowered. In the case of the clad material, the zincate film on the side surface of the substrate can be made uniform and plating adhesion can be prevented from being lowered, and plating peeling can be further suppressed from occurring at the boundary between the core material and the skin material on the side surface of the substrate. Therefore, the Zn content in the aluminum alloy is preferably in the range of 0.005 mass% to 2.000 mass%, and more preferably in the range of 0.100 mass% to less than 2.000 mass%.

(Sodium, strontium, phosphorus)
Na, Sr, and P have the effect of reducing the Si particles in the aluminum alloy substrate and improving the plating properties. In addition, there is an effect of reducing the non-uniformity of the size of the Si particles in the aluminum alloy substrate and reducing the rigidity variation in the aluminum alloy substrate. Therefore, in the aluminum alloy, preferably 0.001% by mass to 0.100% by mass Na, preferably 0.001% by mass to 0.100% by mass Sr, preferably 0.001% by mass to 0%. 1 or 2 or more elements selected from the group consisting of 100% by mass or less of P may be selectively added. However, if each of Na, Sr, and P is less than 0.001% by mass, the above effect cannot be obtained. On the other hand, even if each of Na, Sr, and P is contained in excess of 0.100%, the effect is saturated and no further significant improvement effect can be obtained. In addition, when Na, Sr, and P are added, the content of each of Na, Sr, and P is more preferably in the range of 0.003% by mass to 0.025% by mass.

(Titanium, boron)
Ti and B form borides such as TiB ₂ or Al ₃ Ti in the solidification process during casting, and these become crystal grain nuclei, so that the crystal grains can be refined. This improves the plating properties. In addition, there is an effect of improving the rigidity of the aluminum alloy substrate. However, if the total content of Ti and B is less than 0.005% by mass, the above effect cannot be obtained. On the other hand, even if the total content of Ti and B exceeds 0.500% by mass, the effect is saturated and no further significant improvement effect can be obtained. for that reason. The total content of Ti and B in the case of adding Ti and B is preferably in the range of 0.005% by mass to 0.500% by mass, and in the range of 0.010% by mass to 0.100% by mass. More preferred.

(Other elements)
The balance of the aluminum alloy according to the embodiment of the present invention is made of aluminum and unavoidable impurities. Here, inevitable impurities (for example, V and the like) are each 0.03% or less and a total of 0.15% or less, the characteristics of the aluminum alloy substrate obtained in the present invention are not impaired. .

(Composition of skin material)
Next, the alloy components of the cladding material of the clad material constituting the aluminum alloy substrate for magnetic disks according to the embodiment of the present invention and the content thereof will be described.

In the aluminum alloy substrate according to the embodiment of the present invention, it is possible to obtain excellent smoothness of the plating surface only with the bare material, but plating is performed by attaching a skin material with few second phase particles to both surfaces of the core material. The surface becomes smoother.

In the aluminum alloy substrate according to the embodiment of the present invention, the skin material may be either pure Al or Al—Mg alloy. Pure Al and Al—Mg alloys have fewer coarse second phase particles than other alloys, and are excellent in plating properties.

The pure Al skin material used for the aluminum alloy substrate according to the embodiment of the present invention includes 0.005 mass% to 0.600 mass% Cu, 0.005 mass% to 0.600 mass% Zn, and And 0.001 mass% or more and 0.300 mass% or less of Si and 0.001 mass% or more and 0.300 mass% or less of Fe, and the remaining Al and inevitable impurities are preferable. .

The skin material of the Al—Mg alloy used for the aluminum alloy substrate according to the embodiment of the present invention includes Mg of 0.3% by mass or more and 8.0% by mass or less, and 0.005% by mass or more and 0.600% by mass or less. Cu, 0.005 mass% to 0.600 mass% Zn, 0.010 mass% to 0.300 mass% Cr, and 0.001 mass% to 0.300 mass% Si And 0.001 mass% or more and 0.300 mass% or less of Fe, and what is composed of the balance Al and inevitable impurities is preferable.

(Distribution state of second phase particles of aluminum alloy substrate for magnetic disk)
Next, the distribution state of the second phase particles in the core material and the bare material of the clad material of the aluminum alloy substrate for a magnetic disk according to the embodiment of the present invention will be described.

The second phase particles having the longest diameter of 3 μm or more and 100 μm or less have an effect of improving the rigidity of the aluminum alloy substrate. In embodiments of the present invention, in a metal structure of the core or bare material of the clad material, second phase particles having a longest diameter of 3μm or more 100μm or less, 100 / mm ² or more 50000 / mm ² or less distribution It is preferable to disperse at a density. Sufficient rigidity can be further obtained by dispersing the second phase particles having the longest diameter of 3 μm or more and 100 μm or less at a distribution density of 100 particles / mm ² or more. Further, in the core material of the clad material or the metal structure of the bare material, the second phase particles having the longest diameter of 3 μm or more and 100 μm or less are dispersed at a distribution density of 50000 particles / mm ² or less. During the zincate treatment, it is possible to prevent the second phase particles from dropping and generating a large depression during cutting or grinding, and it is possible to further suppress the deterioration of the smoothness of the plating surface. In addition, in the clad material, the second phase particles on the side surface of the substrate are prevented from falling off during etching, zincate processing, and cutting, and a large depression is generated, and plating peeling occurs at the boundary between the core material and the skin material on the side surface of the substrate. This can be further suppressed. Therefore, during the metal structure of the core or bare material of the clad material, that the second phase particles having a longest diameter of 3μm or more 100μm or less are dispersed in a distribution density of 100 pieces / mm ² or more 50000 / mm ² or less preferably It is more preferable to disperse at a distribution density of 1000 / mm ² or more and less than 30000 / mm ² . In addition, if the longest diameter of the second phase particles existing in the aluminum alloy substrate is less than 3 μm, the dent generated by the second phase particles is not regarded as a problem, and is excluded from the distribution density target.

Moreover, it is preferable that the 2nd phase particle of the longest diameter exceeding 100 micrometers which exists in an aluminum alloy substrate is 0 piece / mm < ² >. If the number of second phase particles having a longest diameter exceeding 100 μm is 1 / mm ² or more, the second phase particles drop off during etching, zincate treatment, cutting or grinding in the bare material, and a large dent is generated. There is a possibility that a smooth plating surface cannot be obtained. In addition, in the clad material, the second phase particles on the side surface of the substrate may fall off during etching, zincate processing, or cutting, and a large dent may be generated, and plating peeling may occur at the boundary between the core material and the skin material on the side surface of the substrate. . In the present invention, the longest diameter refers to the maximum value of the distance between one point on the contour line and another point on the contour line in the planar image of the second phase particles observed with an optical microscope, The maximum value is measured for all points on the contour line, and finally the largest value selected from these maximum values.

(Method of manufacturing aluminum alloy substrate for magnetic disk)
Hereinafter, each process and process conditions of the manufacturing process of the aluminum alloy substrate for magnetic disks which concerns on embodiment of this invention are demonstrated in detail.

A method of manufacturing a magnetic disk using a bare material of an aluminum alloy substrate for a magnetic disk will be described with reference to the flow shown in FIG. Here, the preparation of the aluminum alloy (step S101) to cold rolling (step S105) is a process of manufacturing an aluminum alloy plate, and the production of the disk blank (step S106) to the adhesion of the magnetic substance (step S111) In this process, the manufactured aluminum alloy plate is used as a magnetic disk. First, a process of manufacturing a bare aluminum alloy substrate for a magnetic disk will be described.

First, a molten aluminum alloy having the above component composition is prepared by heating and melting in accordance with a conventional method (step S101). Next, an aluminum alloy is cast from the prepared molten aluminum alloy by a semi-continuous casting (DC casting) method or a continuous casting (CC) method (step S102). The cooling rate during casting is preferably in the range of 0.1 to 1000 ° C./s. When the cooling rate during casting is less than 0.1 ° C./s, the dispersion density of the second phase particles having the longest diameter of 3 to 100 μm exceeds 50000 particles / mm ^2, and the ^second density during etching, zincate treatment, cutting or grinding is the first. There is a possibility that the two-phase particles fall off and a large depression is generated, and the smoothness of the plating surface is lowered. On the other hand, when the cooling rate during casting exceeds 1000 ° C./s, the dispersion density of the second phase particles having the longest diameter of 3 to 100 μm becomes less than 100 particles / mm ² , and sufficient rigidity may not be obtained. Note that the higher the cooling rate during casting, the fine second phase particles are densely distributed and the performance is stabilized. Therefore, the CC method is more preferable as the casting method than the DC casting method. Next, homogenization processing of the cast aluminum alloy is performed (step S103). Homogenization treatment may not be performed, but when it is performed, it is preferably performed at 400 to 500 ° C. for 1 hour or longer. Next, the homogenized aluminum alloy is hot-rolled to obtain a plate material (step S104). In the hot rolling, the conditions are not particularly limited, and the hot rolling start temperature is 300 to 500 ° C., and the hot rolling end temperature is 260 to 400 ° C. Next, the hot-rolled plate is cold-rolled to obtain an aluminum alloy plate having a thickness of about 1.0 mm (step S105). After hot rolling is completed, the product is finished to the required product thickness by cold rolling. The conditions for cold rolling are not particularly limited, and may be determined according to the required product sheet strength and / or sheet thickness, and the rolling rate is 20 to 80%. An annealing treatment may be performed before cold rolling or in the middle of cold rolling to ensure cold rolling processability. When the annealing treatment is performed, for example, in the case of batch heating, it is preferably performed at 300 to 450 ° C. for 0.1 to 10 hours, and in the case of continuous heating, the heating is performed at 400 to 500 ° C. from 0 to It is preferably performed under the condition of holding for 60 seconds.

In order to process the aluminum alloy plate for a magnetic disk, the aluminum alloy plate is punched into an annular shape to create a disk blank (step S106). Next, the disk blank is subjected to pressure annealing at 300 ° C. or higher and 450 ° C. or lower for 30 minutes or more in the atmosphere to create a flattened aluminum alloy substrate (step S107). Next, the aluminum alloy substrate is cut, ground, degreased, and etched (step S108). Next, a zincate process (Zn substitution process) is performed on the surface of the aluminum alloy substrate (step S109). Next, a base treatment (Ni-P plating) is performed on the zincate-treated surface to form an aluminum alloy substrate (step S110). Next, a magnetic material is attached to the surface that has been subjected to the base treatment by sputtering to form a magnetic disk (step S111).

Next, a method of manufacturing a magnetic disk using a clad aluminum alloy substrate for a magnetic disk will be described with reference to the flow shown in FIG. Here, the preparation of the aluminum alloy (step S201) to cold rolling (step S205) is a process of manufacturing an aluminum alloy plate, and the production of the disk blank (step S206) to the adhesion of the magnetic substance (step S211) In this process, the manufactured aluminum alloy plate is used as a magnetic disk.

First, a molten aluminum alloy having the above-described component composition is prepared by heating and melting the core material and the skin material according to a conventional method (step S201). Next, an aluminum alloy is cast from a molten aluminum alloy having a desired composition by a semi-continuous casting (DC casting) method or a continuous casting (CC) method (step S202-1). Next, homogenization treatment of the ingot for skin material is performed, hot rolling to obtain a desired skin material, and a core material having a desired thickness is obtained by chamfering the ingot for core material, on both sides of the core material A step of combining the skin materials to form a laminated material is performed (step S202-2).

When an aluminum alloy substrate for a magnetic disk of a clad material is manufactured by a rolling pressure welding method, an ingot prepared by, for example, a semi-continuous casting (DC casting) method or a continuous casting (CC) method is used as the core material. After casting, if the oxide film is removed by performing mechanical removal such as chamfering or cutting and / or chemical removal such as alkali cleaning, the subsequent pressure contact between the core material and the skin material is made good (step S202-1 and S202-2).

As for the skin material, the ingot obtained by the DC casting method or the CC method is chamfered and hot-rolled to obtain a plate material having a predetermined size. The homogenization treatment may or may not be performed before hot rolling, but when it is performed, it is preferably performed at 350 ° C. or higher and 550 ° C. or lower for 1 hour or longer. In performing hot rolling to make the skin material have a desired thickness, the conditions are not particularly limited. The hot rolling start temperature is 350 ° C. or more and 500 ° C. or less, and the hot rolling end temperature is 260 ° C. It is preferable to set it to 380 degreeC or more. In addition, when the base plate after hot rolling to make the skin material to a desired thickness is washed with nitric acid or caustic soda, the oxide film generated by the hot rolling is removed, and the pressure contact with the core material is made good. (Steps S202-1 and S202-2).

In the embodiment of the present invention, when cladding the core material and the skin material, the cladding ratio of the skin material (ratio of the skin material thickness to the total thickness of the clad material) is not particularly limited, but a necessary product plate It is appropriately determined according to the strength and / or flatness and the grinding amount, and is preferably 3% or more and 30% or less, and more preferably 5% or more and 20% or less. For example, a process of hot rolling to make a skin material with a plate thickness of about 15 mm, and a core material ingot are faced to make a core material with a plate thickness of about 270 mm, and the skin material is combined on both sides of the core material to make a laminated material.

Next, the cast aluminum alloy is homogenized (step S203). When performing the homogenization treatment of the combined material of the core material and the skin material, it is preferable to perform the treatment at a temperature of 400 ° C. or higher and 500 ° C. or lower for 1 hour or longer.

When homogenizing the combined material of the core material and the skin material, it is necessary to suppress the generation of an oxide film at the interface between the core material and the skin material as much as possible. For this purpose, when homogenizing an aluminum alloy having a composition that easily forms an oxide film, for example, an inert gas such as nitrogen gas or argon gas, a reducing gas such as carbon monoxide, or a vacuum such as a vacuum. It is preferably performed in a non-oxidizing atmosphere such as a gas.

Next, the homogenized aluminum alloy is hot-rolled to obtain a plate material (step S204). By performing hot rolling, the core material and the skin material are clad. In performing hot rolling, the conditions are not particularly limited, and the hot rolling start temperature is preferably 300 ° C. or higher and 500 ° C. or lower, and the hot rolling end temperature is preferably 260 ° C. or higher and 400 ° C. or lower. Here, the plate thickness is about 3.0 mm.

The aluminum alloy sheet obtained by hot rolling is finished to a desired product sheet thickness by cold rolling (step S205). The conditions for cold rolling are not particularly limited, and may be determined according to the required product plate strength and / or plate thickness, and the rolling rate is preferably 20% or more and 80% or less.

Annealing treatment may be performed before cold rolling or during cold rolling to ensure cold rolling processability. When the annealing treatment is performed, for example, in the case of batch-type heating, it is preferably performed at 300 ° C. to 450 ° C. for 0.1 hour to 10 hours. Here, the plate thickness is about 1.0 mm.

Each of the above steps is related to the generation of the second phase particles. However, the characteristics of the aluminum alloy substrate for the magnetic disk of the core material according to the embodiment of the present invention are particularly the cooling rate at the time of casting the core material in step S202-1. Has a big influence. The cooling rate at the time of casting the core material is preferably 0.1 ° C./s or more and 1000 ° C./s or less in order to obtain a desired distribution of second phase particles.

When the cooling rate during casting of the core material is less than 0.1 ° C./s, the distribution density of second phase particles having a longest diameter of 3 μm or more and 100 μm or less exceeds 50000 particles / mm ² , during etching, during zincate treatment, during cutting There is a possibility that the second phase particles on the side surface of the substrate drop off and a large depression is generated, and plating peeling occurs at the boundary between the core material and the skin material on the side surface of the substrate. On the other hand, when the cooling rate during casting of the core exceeds 1000 ° C./s, the distribution density of the second phase particles having the longest diameter of 3 μm or more and 100 μm or less becomes less than 100 particles / mm ² , and sufficient rigidity may not be obtained. is there. Therefore, the cooling rate during casting of the core is preferably in the range of 0.1 ° C./s to 1000 ° C./s.

In the embodiment of the present invention, various methods can be applied to clad the core material and the skin material. For example, the rolling press-contact method normally used for manufacture of a brazing sheet etc. is mentioned. In this rolling pressure welding method, homogenization (step S203), hot rolling (step S204), and cold rolling (step S205) are performed in this order on the combined material of the core material and the skin material.

In order to process the aluminum alloy plate of the clad material for a magnetic disk, the processes from disk blank production (step S206) to magnetic material adhesion (step S211) are performed. The process of disk blank production (step S206) to magnetic material adhesion (step S211) is a process of processing a bare aluminum alloy plate for a magnetic disk. Disk blank production (step S106) to magnetic material adhesion This is the same as the step (Step S111).

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

(Aluminum alloy substrate for bare magnetic disk)
First, an example of a bare aluminum alloy substrate for a magnetic disk will be described. Each alloy having the component composition shown in Table 1 and Table 2 was melted in accordance with a conventional method, and a molten aluminum alloy was melted (step S101). In Tables 1 and 2, “-” indicates the measurement limit value or less.

Next, as shown in Tables 3 and 4, Alloy No. A1 to A7, A11 to A36, and AC1 to AC4 are alloy nos. In A8 to A10, a molten aluminum alloy was cast by the CC method to produce an ingot (step S102).

Alloy No. The ingots of A1 to A7, A11 to A36, and AC1 to AC4 were subjected to 15 mm chamfering on both sides. No. The alloys of A1 to A9, A11 to A36, and AC1 to AC4 were subjected to a homogenization treatment at 480 ° C. for 3 hours (step S103). No. The alloys A1 to A8, A11 to A36, and AC1 to AC4 were hot-rolled at a rolling start temperature of 460 ° C. and a rolling end temperature of 340 ° C. to obtain hot rolled sheets having a thickness of 3.0 mm (step S104). No. Hot rolled sheets of A1-A6, A8-A36 and AC1-AC4 alloys are annealed at 400 ° C for 2 hours and rolled to a final thickness of 1.0 mm by cold rolling (rolling ratio 66.7%). Then, an aluminum alloy plate was obtained (step S105). A disk blank was produced by punching the aluminum alloy plate into an annular shape having an outer diameter of 96 mm and an inner diameter of 24 mm (step S106).

The disc blank was subjected to pressure annealing at 400 ° C. for 3 hours (step S107). End face processing was performed to obtain an outer diameter of 95 mm and an inner diameter of 25 mm, and grinding (surface 10 μm grinding) was performed (step S108). Then, after degreasing at 60 ° C. for 5 minutes with AD-68F (manufactured by Uemura Kogyo), etching is performed at 65 ° C. for 1 minute with AD-107F (manufactured by Uemura Kogyo), and 30% HNO ₃ aqueous solution (room temperature ) For 20 seconds. The surface of the disk blank whose surface was adjusted was subjected to a zincate treatment using AD-301F-3X (manufactured by Uemura Kogyo) (step S109). The surface treated with zincate is electrolessly plated with Ni-P to a thickness of 17 μm using an electroless Ni—P plating solution (Nimden HDX (manufactured by Uemura Kogyo)) and then finish-polished with a blanket (polishing amount 4 μm)) Performed (step S110).

Aluminum alloy ingot after casting (step S102) process, aluminum alloy plate after cold rolling (step S105) process, aluminum alloy substrate after grinding process (step S108), and plating treatment polishing (step S110) process The following evaluation was performed on the aluminum alloy substrate.

[Cooling speed during casting]
DAS (Dendrite Arm Spacing) of the ingot after casting (step S102) was measured, and the cooling rate during casting was calculated. DAS was measured by the secondary branch method after observing the cross-sectional structure in the ingot thickness direction with an optical microscope. The measurement used the cross section of the center part of the thickness direction of an ingot.

〔rigidity〕
The aluminum alloy plate after cold rolling (step S105) was heated at 400 ° C. for 3 hours, and then Young's modulus was measured by a resonance method to evaluate rigidity. The measurement of rigidity was performed at room temperature using a JE-RT type apparatus manufactured by Nippon Techno Plus Co., Ltd. Those having a Young's modulus of 75 GPa or higher were evaluated as excellent (（), those having a Young's modulus of 72 GPa or more and less than 75 GPa were evaluated as good (◯), and those having a Young's modulus of less than 72 GPa were determined as poor (×).

[Distribution density of second phase particles with a longest diameter of 3-100 μm and a longest diameter of 100 μm]
The distribution density (particles / mm ² ) of the second phase particles having a longest diameter of 3 to 100 μm and a longest diameter of 100 μm was observed by observing 1 mm ² of the cross section of the aluminum alloy substrate after grinding (step S108) at 400 × with an optical microscope. Second-phase particles having a longest diameter of 3 to 100 μm and a longest diameter of 100 μm were counted to determine the distribution density.

[Smoothness of plating surface]
The surface of the aluminum alloy substrate after Ni-P plating treatment polishing (step S110) was observed with an optical microscope at 1 × ² with a magnification of 500 times, and the number of pits having a longest diameter of 5 μm or more was counted, and the number per unit area (number Density: pieces / mm ² ) was determined. A case where the number of pits is 0 to 10 / mm ² is excellent (marked with ◎), a case where the number of pits is 10 to 20 / mm ² is good (marked with ○), and a case where it exceeds 20 pieces / mm ² is defective (marked with ×). did. The above evaluation results are shown in Tables 5 and 6.

As shown in Tables 5 and 6, in Examples 1 to 43, an aluminum alloy substrate for a magnetic disk having a smooth plating surface and high rigidity was obtained. On the other hand, Comparative Examples 1 to 4 were inferior in the smoothness or rigidity of the plating surface. In Comparative Example 1, the Young's modulus was low and the rigidity was poor because the Si content was small. In Comparative Example 2, since the content of Si was large, a large amount of coarse Si particles were generated, so that the Si particles dropped out during the plating pretreatment, and a large depression was generated. As a result, many pits were generated on the plating surface, and the smoothness of the plating surface was deteriorated. In Comparative Example 3, the Young's modulus was low and the rigidity was poor because the Fe content was small. In Comparative Example 4, a large amount of coarse Al—Fe—Si-based compound was produced due to the high Fe content, and this compound dropped out during the pre-plating treatment, resulting in a large depression. As a result, many pits were generated on the plating surface, and the smoothness of the plating surface was deteriorated.

(Aluminum alloy substrate for clad magnetic disk)
Next, an example of an aluminum alloy substrate for a magnetic disk made of a clad material will be described.

Each alloy having the component composition shown in Tables 7 to 10 was melted in accordance with a conventional method, and a molten aluminum alloy was melted (step S201). Tables 7 and 8 show the core material of the clad material, and Tables 9 and 10 show the component composition of the clad material. In Tables 7 to 10, “-” indicates the measurement limit value or less.

As shown in Table 11 and Table 12, alloy no. The aluminum alloy melts of B1 to B7, B11 to B36, BC1 and BC2 are alloy Nos. For the aluminum alloy melts B8 to B10, ingots were produced by the CC method (step S202-1). The ingot for skin material was produced by the all alloy DC casting method. Alloy No. The core materials B1 to B7, B11 to B36, BC1 and BC2 were chamfered on both sides of the ingot 15 mm to form core materials (step S202-2). The skin material was chamfered 15 mm on both sides of the ingot, homogenized at 520 ° C. for 6 hours in the atmosphere, hot-rolled, and alloy No. C1 to C7, C11 to C36, CC1 and CC2 are hot-rolled plates having a thickness of 15 mm. C8 to C10 were hot-rolled plates having a thickness of 0.5 mm. Thereafter, the hot-rolled sheet was washed with caustic soda to make a skin material, and the skin material was combined on both sides of the core material to make a laminated material. Next, the homogenization process was performed at 480 degreeC for 3 hours (step S203). Hot rolling was performed at a rolling start temperature of 460 ° C. and a rolling end temperature of 340 ° C. to obtain a hot rolled plate having a thickness of 3.0 mm (step S204). Alloy No. Hot rolled sheets other than B7 and C7 alloys were annealed at 400 ° C. for 2 hours, and rolled to a final sheet thickness of 1.0 mm by cold rolling (rolling rate: 66.7%) to obtain an aluminum alloy sheet. (Step S205). The aluminum alloy plate was punched out into an annular shape having an outer diameter of 96 mm and an inner diameter of 24 mm to produce a disc blank (step S206).

The disc blank was subjected to pressure annealing at 400 ° C. for 3 hours (step S207). End face processing was performed to obtain an outer diameter of 95 mm and an inner diameter of 25 mm, and grinding (surface 10 μm grinding) was performed (step S208). Then, after degreasing at 60 ° C. for 5 minutes with AD-68F (manufactured by Uemura Kogyo), etching is performed at 65 ° C. for 1 minute with AD-107F (manufactured by Uemura Kogyo), and 30% HNO ₃ aqueous solution (room temperature ) For 20 seconds. The surface of the disk blank whose surface was adjusted was subjected to double zincate treatment using AD-301F-3X (manufactured by Uemura Kogyo) (step S209). The surface treated with zincate is electrolessly plated with Ni-P to a thickness of 17 μm using an electroless Ni—P plating solution (Nimden HDX (manufactured by Uemura Kogyo)) and then finish-polished with a blanket (polishing amount 4 μm)) Performed (step S210).

The ingot after the casting (step S202-1) process, the aluminum alloy plate after the cold rolling (step S205) process, the aluminum alloy substrate after the grinding process (step S208), and the plating treatment polishing (step S210) ) The following evaluation was performed on the aluminum alloy substrate after the process.

[Cooling rate during casting of core material ingot]
The DAS of the ingot after casting (step S202-1) was measured, and the cooling rate during casting was calculated. DAS was measured by the secondary branch method after observing the cross-sectional structure in the ingot thickness direction with an optical microscope. The measurement used the cross section of the center part of the thickness direction of an ingot.

Evaluation of rigidity, distribution of the second phase particles having the longest diameter of 3 to 100 μm and the longest diameter of 100 μm in the core material, and the smoothness of the plating surface were performed in the same manner as the bare material. The above evaluation results are shown in Table 13 and Table 14.

As shown in Table 13 and Table 14, in Examples 44 to 86, aluminum alloy substrates for magnetic disks having smooth plating surfaces and high rigidity were obtained. On the other hand, both Comparative Example 5 and Comparative Example 6 were inferior in rigidity. In Comparative Example 5, the Young's modulus was low and the rigidity was poor because the Si content was low. In Comparative Example 6, the Young's modulus was low and the rigidity was poor because the Fe content was small.

The present invention is capable of various embodiments and modifications without departing from the broad spirit and scope of the present invention. The above-described embodiments are for explaining the present invention and do not limit the scope of the present invention. In other words, the scope of the present invention is shown not by the embodiments but by the claims. Various modifications within the scope of the claims and within the scope of the equivalent invention are considered to be within the scope of the present invention.

This application is based on Japanese Patent Application No. 2014-223387 filed on October 31, 2014. The specification, claims, and entire drawings of Japanese Patent Application No. 2014-223387 are incorporated herein by reference.

The present invention is preferably used for a magnetic disk of a computer storage device, for example.

Claims (7)

0.5 mass% or more and 24.0 mass% or less of Si;
0.01 mass% or more and 3.00 mass% or less of Fe;
Containing
It consists of the balance Al and inevitable impurities,
An aluminum alloy substrate for a magnetic disk. 0.005 mass% or more and 2.000 mass% or less of Cu,
Mg of 0.1% by mass or more and 6.0% by mass or less,
0.1 mass% or more and 2.0 mass% or less of Ni,
0.01 mass% or more and 2.00 mass% or less of Cr,
0.01% by mass or more and 2.00% by mass or less of Mn,
0.001 mass% or more and 0.100 mass% or less of Na,
0.001 mass% or more and 0.100 mass% or less of Sr,
0.001 mass% or more and 0.100 mass% or less of P,
Further containing one or more elements selected from the group consisting of:
The aluminum alloy substrate for a magnetic disk according to claim 1. 0.005 mass% or more and 2.000 mass% or less of Zn,
Further containing,
3. The aluminum alloy substrate for a magnetic disk according to claim 1, wherein the aluminum alloy substrate is used. Ti and B whose total content is 0.005% by mass or more and 0.500% by mass or less,
Further containing,
The aluminum alloy substrate for a magnetic disk according to claim 1, wherein the aluminum alloy substrate is a magnetic disk. The second phase particles having a longest diameter of 3μm or more 100μm or less, dispersed in a 100 / mm ² or more 50000 / mm ² or less in the distribution density,
The aluminum alloy substrate for a magnetic disk according to any one of claims 1 to 4, wherein the aluminum alloy substrate is used. Containing the second phase particles, the longest diameter of the second phase particles is 100 μm or less,
6. The aluminum alloy substrate for a magnetic disk according to claim 1, wherein the aluminum alloy substrate is a magnetic disk. Clad material made of pure Al or Al-Mg alloy is clad on both sides.
7. The aluminum alloy substrate for a magnetic disk according to claim 1, wherein the aluminum alloy substrate is a magnetic disk.

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